Creep rupture assessment by a robust creep data interpolation using the linear matching method

The accurate assessment of creep rupture limit is an important issue for industrial components under combined action of cyclic thermal and mechanical loading. This paper proposes a new creep rupture assessment method under the Linear Matching Method framework, where the creep rupture limit is evaluated through an extended shakedown analysis using the revised yield stress, which is determined by the minimum of the yield stress of the material and the individual creep rupture stress at each integration point. Various numerical strategies have been investigated to calculate these creep rupture stresses associated with given temperatures and allowable creep rupture time. Three distinct methods: a) linear interpolation method, b) logarithm based polynomial relationship and c) the Larson–Miller parameter, are introduced to interpolate and extrapolate an accurate creep rupture stress, on the basis of discrete experimental creep rupture data. Comparisons between these methods are carried out to determine the most appropriate approach leading to the accurate solution to the creep rupture stresses for the creep rupture analysis. Two numerical examples including a classical holed plate problem and a two-pipe structure are provided to verify the applicability and efficiency of this new approach. Detailed step-by-step analyses are also performed to further confirm the accuracy of the obtained creep rupture limits, and to investigate the interaction between the different failure mechanisms. All the results demonstrate that the proposed approach is capable of providing accurate but conservative solutions.